Will I lose my notes if I uninstall Evernote?

When upgrading any of your Evernote programs, Evernote's local database and all your notes are left intact.

If you uninstall Evernote, your database of notes on that device will be removed as part of the uninstall process. If, however, you have opted to create any local (that is, non-synced) notebooks, it's important to back these up before uninstalling Evernote or they will be lost.